PostgreSQL to MySQL migration?

PostgreSQL and MySQL are not 100% compatible. So will everything be just Plug-and-Play or are the things, you should pay special attention, if you are migrating your system from PostgreSQL to MySQL? In my mind are especiially SQL query syntax checks and options to be set while doing SQL db backup from PostgreSQL/restore to MySQL.

I have been mostly working on MySQL/MS SQL and I have not worked with PostgreSQL.